BIOLOGICAL CONTROL OF PESTS AND PLANT DISEASES
Year:2014 | Volume:3 | Issue:1|Papers Count:8

Insects are poikilothermes and hence environmental factors and primarily temperature can affect their biological activities and behavior. In this study thermal range preferred by Ooencyrtus fecundus Ferrier & Voegele was investigated by a device producing a thermal gradient from 16 to 47ºC. Temperature of different parts of the arena was precisely recorded by eight thermometers entered the arena from marginal walls of the apparatus. Three entries were prepared in cold, middle and warm areas of the device. In order to exclude possible tendencies of the release point, experiment was done three times each from an entry. Twenty wasps were released each time and number of the parasitoids as well as current temperature of any part was recorded after 5, 15 and 30 minutes. The highest frequency of the wasp (89.25%) was occurred in a spectrum of 23.47-29.54ºC while 46.66% of them were assembled in center of the arena where mean temperature was 26.03ºC. Wasps' distribution was affected by release point as significant discrepancies observing between all pairs of the experiments. The results revealed that the wasp searches for the sites with desirable temperatures by limited locomotion but avoid further movements as soon as it finds tolerable temperature.

The objective of the present study was to optimize a wettable powder formulation for two Iranian Bt strains (YD5 and KH4) in order to enhance efficiency and durability of the final products as biological agent against lepidopteran and coleopteran pests. Massproduction of the mentioned strains was done in a batch fermenter based on the previouslyoptimized economical medium and fermentation conditions. The final concentration was achieved 6 ×109 (CFU/mg). To optimize formulation for two strains, 25% spore crystal mixture of the strain and 75% adjuvants including different fillers, surfactants, materialsenhancing durability, anti UV materials, suspensors, wetters, palatability materials and antimicrobial materials in the framework of five statistical treatments were used. Based on the results, the treatment containing milk powder (4%), perlite (6%), irosile (2%), sodiumloril sulfate (8%), alkaline naphthalene (20%), starch (10%), gelatin (9%), sugar (10%), potassium surbate (1%), casein and gluten (2%), potassium dioxide (3%) and monosodiumglutamate (0.2%) showed maximum suspensibility (73 and 71%) and wettability (25 and24%) for YD5 and KH4 strains, respectively, and selected for the next experiments. Theselected formulation for both strains had a white to grey color, 6-7% moisture content, andpH 6.1 and 6.2. Crystals in both formulations were stable without any changes during oneyear. The LC50 of the selected formulation for YD5 and KH4 strains against larvae cottonbollworm and elm leaf beetle was 550 and 510 ng/cm2 leaf, respectively.

The green lacewing, Chrysoperla carnea (Stephens) is one of the important predators ofmany pests including Helicoverpa armigera (Hübner) and Tetranychus urticae Koch. Ininsectaries, the larvae of this predator are mainly reared on Anagasta kuehniella egg. In thisresearch, biological and life table parameters of C. carnea in feeding on A. kuehniella eggas a laboratory prey and two natural preys including H. armigera (stages of egg andneonate larva) and T. urticae were studied. The experiments were carried out at 26±1oC, 70±5% RH and 16: 8 (L: D) h. C. carnea larvae reared on T. urticae did not survive toadult hood. The maximum longevity of adult females (38.3 day), oviposition period (32.33 day) and eggs/female/day (30.52) were obtained in rearing of the predator on H. armigeraegg. Survivorship curve of the predator on all insect preys was from type I. Netreproductive rate (R0) and intrinsic rate of increase (r) of C. carnea on A. kuehniella eggand H. armigera egg and neonate larva were estimated to be 352.68, 579.64 and 385.47 pergeneration and 0.1816, 0.2152 and 0.2094 d-1, respectively.

Pathogenicity of Beauveria bassiana strain DEBI001, Lecanicillium muscarium strain DAOM 198499 and their combination was investigated on 2nd nymphs and adults of B. tabaci in controlled condition (in 23±1ºC, 95±5% and 16: 8 L: D). Five concentrations from each isolates were sprayed on undersides of young eggplant leaves that involved 2ndnymphs. Experiments were carried out on adults with the same concentrations in two methods of spraying: Direct spraying on adults, and indirect spraying on plant leaves. LC50 values of the B. bassiana, L. muscarium and their combination on 2nd nymphs was 4.4×105, 1.8×105 and 7.9×105 conidia/ml., respectively. The results showed that LT50values for different concentrations (106, 107 and 108 conidia/ml.) of B. bassiana were 8.3, 6 and 4.8 days; for L. muscarium were equal to 7.2, 5.5 and 3.9 days and 6.7, 5.1 and 4 daysfor their combination. In indirect application methods of isolates on host plant, highmortality rate of cotton whitefly adults was happened than control. The highest mortalitydue to B. bassiana was 89.33%; and 96.25%; while it was 78.33 % and 93.75% due to L. muscarium, immediately and 5 days after spraying, respectively. Adult mortality rate waslower in direct spraying method than indirect application (51.1% by B. bassiana and38.32% by L. muscarium by 108 conidia/ml.).

One of the new methods for plant diseases management is application of plant extracts.Soilborne pathogens fungal are world wide distributed and important phytopathogens. They cause yield losses in tobacco growing countries. The purpose of this study is to evaluate the antifungal activity of plant extracts on soilborne pathogens fungal of tobacco (Rhizoctoniasolani and Phytophthora nicotianae) and determine the best concentration of extracts on antifungal activity. The experiment was done in a factorial design based on completely randomized with three factors and five replications under in vitro condition. The first factors, plant extract (nine plant species), the second factor, solvent (five solvent) and the third factor, concentration (three concentration) were considered. In our previous study, experiments were carried out in pot condition based on factorial design with eight eentreatments and three replications in Tirtash Reaserch and Education Center, in 2013. In this study, the first factor including three plant extracts (catmint, tobacco and thyme), these cond factor, three concentration (0.5, 1 and 2 in 1000), and the third factor, treatment application of method two (spray and drench) were considered. The results indicated that different concentration of crude extracts of catmint, tobacco, thyme, fennel, hyssop and badrashbi have remarkable antifungal activity on the fungi. Methanol is perfect solvent for extraction of antifungal compounds. The maximum inhibitory concentration of eachextracts was 2000 ppm. The results of analysis variance showed that the effect of plant extracts on control of soilborne pathogens fungal of tobacco was significant at 1% level. Inour study, the interactions of "plant extracts × concentration", "concentration × application method" and also, "plant extracts × concentration × application method" was significant at1% level. Comparison of treatments means showed that extracts of both plant (catmit andtobacco) at 0.2% concentration were the best treatments with 80% and 75% inhibition off ungi, respectively.

The green peach aphid, Myzus persicae (Hem: Aphididae) is a polyphagus aphid specie sinfecting over 400 plants species belonging to 40 different families. The Oenopiaconglobata contaminata (Col.: Coccinellidae) is one of the most important predator oforchard pests in Iran. In this study, efficiency and predatory of this predator on green peachaphid M. persicae was evaluated under laboratory conditions (55±5% r.h. and a 16: 8 hphotoperiod). The effect of host accumulation to amount of reproduction of this ladybirdwas studied for 21 days. The result showed that accumulation of 40 hosts was regarded asthe lowest density that the ladybird will be required to grow. Data were analyzed with SASstatistical software. Logistic regression was used to determine type of functional responseand nonlinear regression to estimate parameters of searching efficiency (a) and handlingtime (Th). The result showed that the functional response was type II. Searching efficiencyand handling time were 0.063±0.00819 h-1 and 0.1425±0.029 h, respectively. Predationrates of forth instar male and female were 45.22, 29.65 and 50.70, respectively. Our resultsindicated that the O. conglobata may be a useful candidate for the biological control of M.

To evaluate the effect of Metarhizium an isopliae and Trichoderma harzianum on rootknot nematode (Meloidogyne javanica) in tomato, experiments was performed under controlled as well as greenhouse conditions. Volatile and non-volatile tests showed that there is no inhibitory effect against every one of each biocontrol agents. On the larvalmortality and inhibition of egg hatching, a laboratory test was performed in a completely randomized design with eight treatments in four replicates. It has been shown that whole treatments have significantly different with control. The best treatment that cause dmaximum larval mortality was T. harzianum culture filtrate, and the most effective treatment in egg hatch inhibition was M. an isopliae culture filtrate. There was nosignificant effect of mixture of suspensions and culture filtrates of both biocontrol agents. Agreenhouse test was performed in a completely randomized design with five treatments infour replicates. In this test, T. harzianum increased growth of plants in comparison to inoculated and inoculated controls. M. anisopliae improved the growth factors in comparison to negative control, but not in positive control. Both bioagents considerablydecreased the nematode-related factors including root gall. M. anisopliae had more effecton nematode-related factors than T. harzianum. Under greenhouse condition, there was nosignificant effect of the mixture of both fungi against the tested nematode.

Chemical fungicides are considered as the primary approach for controlling postharve stfungal decay of fruit and vegetables, while continuous use of fungicides has faced to increasing public concern regarding contamination of perishables with fungicidal residues, and proliferation of resistance in the pathogen populations. So, recent researches in this area have focused on the development and evaluation of alternative control strategies toreduce dependency on synthetic fungicides. Thus, in this research in vitro and in vivobiocontrol activity of plant essential oils of Satureja hortensis, Rosmarinus officinalis, Mentha piperita, Zataria multiflora and Cuminum cyminum against the growth of Botry tiscinerea, the causal agent of apple gray mold was evaluated. In vitro results revealed that the essential oils of Zataria multiflora, Cuminum cyminum and Mentha piperita have thehighest biocontrol activity among tested essential oils. In vivo results also indicated that those essential oils in a concentration of 1000 ppm have a significant inhibitory effect onthe growth of Botrytis cinerea. GC-MS analysis demonstrated that carvacrol (71.19%), ɤ-Terpinene (30.41%) and menthol (51.19%) were the main components of the essential oilsof Zataria multiflora, Cuminum cyminum and Mentha piperita, respectively. Based on theresults, the essential oils could be suggested as an alternative to synthetic chemicals.